Ink jet printing apparatus

ABSTRACT

Ink jet printing apparatus includes a linear array of jet modules each having an inlet for receiving ink, an outlet for re-circulating the ink, a nozzle for discharging ink in the form of droplets, and a perturbation device for causing a continuous stream of ink droplets to be discharged from the respective nozzle. The apparatus further includes an ink supply system having an inlet manifold, an outlet manifold, and a plurality of connecting passageways connecting the jet modules in parallel between the inlet and outlet manifolds. The connecting passageways connect the inlet of each jet module to the inlet manifold and the outlet of each jet module to the outlet manifold, such as to define a T-connection of each jet module with the inlet and outlet manifolds. Such a construction reduces the mass of each jet module thereby permitting printing at higher frequencies and with smaller ink droplets.

The present invention relates to ink jet printing apparatus of the typedescribed in our prior U.S. Pat. Nos. 5,969,733, 6,003,980 and6,106,107, and also in our prior International Patent Application No.PCT/IL02/00346 filed May 3, 2002, published on Nov. 14, 2002 asInternational Publication No. WO 02/090119 A2, the contents of whichpatents and application are incorporated herein by reference.

Ink jet printers are based on forming droplets of liquid ink andselectively depositing the ink droplets on a substrate. The known inkjet printers generally fall into two categories: drop on-demandprinters, and continuous-jet printers. Drop on-demand printersselectively form and deposit the ink jet droplets on the substrate asand when demanded by a control signal from an external data source;whereas continuous-jet printers are stimulated by a perturbation device,such as piezoelectric transducer, to form the ink droplets from acontinuous ink jet filament at a rate determined by the perturbationdevice.

In continuous-jet printers, the droplets are selectively charged anddeflected to direct them onto the substrate according to the desiredpattern to be printed. In binary-type printer systems, the droplets areeither charged or uncharged and, accordingly, either reach or do notreach the substrate at a single predetermined position. In a multi-levelsystem, the droplets can receive a large number of charge levels and,accordingly, can generate a large number of print positions. Both typesof systems generally include a gutter for receiving the ink droplets notto be printed on the substrate.

The present invention is particularly applicable to continuous-jetprinters and is therefore described below with respect to thisapplication. It will be appreciated, however, that aspects of theinvention could also be used in droplet-on-demand printers or in otherapplications.

The conventional continuous-jet printer of the type described in theabove-cited patents and International Application comprises a lineararray of jet modules each including an inlet for receiving: ink, anoutlet for re-circulating the ink, a nozzle for discharging ink in theform of droplets, and a perturbation device, such as a piezoelectrictransducer, for causing a continuous stream of droplets to be dischargedfrom the respective nozzle. Such apparatus further comprises an inksupply system including an inlet manifold, an outlet manifold, and aplurality of connecting passageways connecting the jet module inlets inparallel between the inlet and outlet manifolds. In one prior artconstruction of such printing apparatus, the connecting passagewaysdefine an F-connection of each jet module with the inlet and outletmanifolds.

Such a prior art construction is more particularly described below withrespect to FIGS. 1-4 of the accompanying drawings. One drawback in sucha prior art construction is that the jet modules have relatively largemass which undesirably affects the printing resolution. Thus, for highquality printing, it is desirable to print with very small ink droplets,at relatively high frequencies, and with relatively close spacingsbetween the jet modules. Jet modules with relatively high masses, suchas in the prior art construction illustrated in FIGS. 1-4, limit allthree of the above objectives for high quality printing.

Another drawback in the prior art construction illustrated in FIGS. 1-4is the tendency of the nozzles to become clogged, and the difficulty incleaning the nozzles at the printing site without requiring majordisassembly of the jet modules.

OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION

An object of the present invention is to provide jet printing apparatushaving advantages in one or more of the above respects.

According to one aspect of the present invention, there is provided anink jet printing apparatus comprising: a linear array of jet moduleseach including an inlet for receiving ink, an outlet for re-circulatingthe ink, a nozzle for discharging ink in the form of droplets, and aperturbation device for causing a continuous stream of ink droplets tobe discharged from the respective nozzle; and an ink supply systemincluding an inlet manifold, an outlet manifold, and a plurality ofconnecting passageways connecting the jet modules in parallel betweenthe inlet and outlet manifolds; characterized in that the connectingpassageways connect the inlet of each jet module to the inlet manifoldand the outlet of each jet module to the outlet manifold, such as todefine a T-connection of each jet module with the inlet and outletmanifolds.

As will be described more particularly below, such a construction,wherein a T-connection rather than an F-connection is made of each jetmodule with the inlet and outlet manifolds, enables a significantreduction in the mass of each jet module, as well as a closer spacingbetween jet modules, to be made such as to enhance the printing quality.

In the described preferred embodiments, each of the jet modules has avertically-extending longitudinal axis, and the inlet and outletmanifolds both have longitudinal axes extending horizontally, parallelto each other in a common horizontal plane on opposite sides of the jetmodules.

According to further features in the described preferred embodiments,the linear array of jet modules is carried by a mounting device formedwith the inlet and outlet manifolds. More particularly, each of the jetmodules is formed with a T-shaped connecting passageway having ahorizontal leg communicating at its opposite ends with the inlet andoutlet manifolds, and a vertical leg centrally off the horizontal legand leading to its respective nozzle.

According to further features in the described preferred embodiments,the perturbation device for each jet module is a piezoelectrictransducer, and each jet module is further formed with a mounting forthe piezoelectric transducer above the jet module inlet. In addition,each jet module further includes a counterweight supported thereon abovethe piezoelectric transducer.

According to one described preferred embodiment, the mounting device isformed with a linear array of bores receiving the linear array of jetmodules with the inlet and outlet manifolds of the mounting memberlocated on opposite sides of the jet modules.

According to a second described preferred embodiment, the mountingdevice includes two sections secured together with the array of jetmodules inbetween. One of the sections includes the inlet manifold inthe form of a continuous channel plugged at its opposite ends, and theother section includes the outlet manifold also in the form of acontinuous channel plugged at its opposite ends. Each of the sections isformed with an opening for each of the jet modules and includes a pin ineach opening formed with a connecting passageway connecting therespective manifold to the respective side of the jet module.

Preferably, the two sections of the mounting device are made of aplastic material having a relatively low mass (as compared to metal).Such a construction enables the mass of the jet modules to be reduced,thereby permitting the printing to be effected with small ink dropletsat relatively high frequencies for purposes of enhancing the printingquality; at the same time such a construction permits the jet modules tohave a relatively large space between them if desired in order to reducethe overall cost of the printer apparatus.

According to another aspect of the present invention, there is providedan ink jet printing apparatus, comprising: a linear array of jet moduleseach including an inlet for receiving ink, an outlet for re-circulatingthe ink, a nozzle for discharging ink in the form of droplets, and aperturbation device for causing a continuous stream of ink droplets tobe discharged from the respective nozzle; and an ink supply systemincluding an inlet manifold, an outlet manifold, and a plurality ofconnecting passageways connecting the jet modules in parallel betweenthe inlet and outlet manifolds; each of the nozzles being removablyattached to the jet module by a coupling sleeve which permits convenientdetaching of the nozzle for cleaning purposes. The foregoing featuresenable each nozzle to be conveniently disassembled and cleaned as andwhen needed at the printing site, and thereby obviate the need for largedown times or removal of the apparatus from the printing site forcleaning purposes. The foregoing features enable each nozzle to beconveniently disassembled and cleaned as and when needed at the printingsite, and thereby obviate the need for large down times or removal ofthe apparatus from the printing site for cleaning purposes.

According to a further aspect of the present invention, there isprovided ink jet printing apparatus comprising a linear array of jetmodules each including an inlet for receiving ink, an outlet forre-circulating the ink, a nozzle for discharging ink in the form ofdroplets, and a perturbation device for causing a continuous stream ofink drops to be discharged from the respective nozzle. Each of the jetmodules is equally spaced from each other in the linear array. Theapparatus further comprises an ink supply system including an inletmanifold, an outlet manifold, and a plurality of connecting passagewaysconnecting the jet modules in parallel between the inlet and outletmanifolds; and a gutter in every other space between the jet modulessuch that each gutter is shared by two jet modules on its oppositesides. The foregoing features not only decrease the cost of the printingapparatus but also enable the printing apparatus to be constructed morecompactly, thereby enhancing printing quality.

Further features and advantages of the invention will be apparent fromthe description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described herein, by way of example only, withreference to the accompanying drawings, wherein:

FIGS. 1-4 illustrate a known prior art construction of jet printingapparatus, FIG. 1 being a three-dimensional view of the printer headassembly in such apparatus, FIG. 2 being a side elevational view of FIG.1, FIG. 3 being a longitudinal sectional view through one jet module,and FIG. 4 diagrammatically illustrating the arrangement of guttersbetween jet modules;

FIGS. 5, 6, 7 and 8 are views corresponding to FIGS. 1, 2, 3 and 4,respectively, illustrating one embodiment of ink jet printing apparatusconstructed in accordance with the present invention;

FIGS. 9-12 illustrate a second embodiment of ink jet printing apparatusconstructed in accordance with the present invention, FIG. 9 being anexploded view of the printer head assembly, FIG. 10 being a sectionalview through one jet module, FIG. 11 being an enlarged fragmentary viewof a portion of FIG. 10, and FIG. 12 being a sectional view along lineXII-XII of FIG. 10; and

FIG. 13 illustrates a jet module constructed in accordance with a thirdembodiment of the invention.

It is to be understood that the foregoing drawings, and the descriptionbelow, are provided primarily for purposes of facilitating understandingthe conceptual aspects of the invention and various possible embodimentsthereof, including what is presently considered to be a preferredembodiment. In the interest of clarity and brevity, no attempt was madeto provide more details than necessary to enable one skilled in the art,using routine skill and design, to understand and practice the describedinvention. It is to be further understood that the embodiments describedare for purposes of example only, and that the invention is capable ofbeing embodied in other forms and applications than described herein.

Prior Art Construction of FIGS. 1-4

FIGS. 1-4 illustrate a printer head assembly of a known prior artconstruction used in continuous-jet printers. As shown particularly inFIG. 1, the illustrated printer head assembly includes a common mountingmember 2 mounting a linear array of jet modules 3 along equally-spacedvertical axes. As shown particularly in FIG. 3, each jet module 3includes a nozzle inlet 4 for receiving ink, a nozzle 5 for dischargingink in the form of droplets, and a perturbation device 6 for causing acontinuous stream of ink droplets to be discharged from the respectivenozzle 5.

The ink is supplied to all the jet modules in parallel from a commonreservoir (not shown). For this purpose, the common mounting member 2 isformed with an inlet manifold 7 a (FIG. 1) and an outlet manifold 7 b.Inlet manifold 7 a is connected to the inlet 8 of each jet moduleleading to its nozzle inlet 4. Each jet module further includes apassageway 9 leading from the nozzle inlet 4 to the jet module outlet 10for re-circulating the ink to the outlet manifold 7 b.

In the prior art construction illustrated in FIGS. 1-4, the connectingpassageways 8, 9, 10 define an F-connection of each jet module with theinlet manifold 7 a and outlet manifold 7 b of mounting member 2. Thus,as shown in FIG. 1, the two manifolds 7 a, 7 b are vertically alignedwith each other; similarly, the inlet 8 and outlet 10 of each jet module3 are vertically aligned with each other and are connected together bypassageway 9. In the assembly of jet modules, the common mounting member2 extends laterally of the line of jet modules 3, with the inletmanifold 7 a communicating with the inlet 8 of each jet module, and theoutlet manifold 7 b communicating with the outlet 10 of each jet module.The jet modules are thus connected in parallel to the inlet manifold 7 aand outlet manifold 7 b via F-connections each defined by the horizontalinlet 8, the vertical connecting passageway 9, and the horizontal outlet10, as shown particularly in FIG. 3.

Passageways 8, 9, 10 of each jet module 3 are formed in a body member 11of each jet module 3. In the illustrated construction, the nozzle 5 isfixed to the lower end of a holder 12 threadedly received at 13 in thelower end of body member 11 of the respective jet module. The nozzleinlet 4 communicates with nozzle 5 via a passageway 14 extending throughthe nozzle holder 12. The nozzle holder further includes a filter 15 forremoving solid particles from the liquid supplied to the nozzle, and anO-ring 16 for sealing the coupling between body member 11 and the nozzleholder 12.

The opposite end of body member 11 of each jet module 3 is formed with avertically-extending stem 17 for mounting the perturbation device 6 ofthe respective jet module. In the illustrated construction, theperturbation device 6 is a piezoelectric transducer electrically drivenby an electrode 18 connected to a voltage source (not shown), andgrounded via the jet module, which is of metal. Stem 17 further mounts acounter-weight 19 separated from the piezoelectric transducer 6 by aseparator disc 20.

In the prior art printing apparatus illustrated in FIGS. 1-4, the lineararray of jet modules 3 are equally spaced from each other; and a gutter30 (FIG. 4) is provided in each of the spaces between the nozzles, asshown in FIG. 4. Thus, during the operation of the ink jet printer, asdescribed more particularly in the above-cited patents and InternationalApplication incorporated herein by reference, the piezoelectrictransducer 6 of each jet module causes each nozzle to discharge acontinuous stream of ink droplets towards the substrate 32. Each of theink droplets is charged and deflected (by electrodes not shown herein)to its proper location on the substrate according to the data to beprinted; and if a mark is not to be printed, the droplet is deflected toits respective gutter 30 located laterally of nozzle 5 of the respectivejet module.

As briefly described earlier, the prior art ink jet printer illustratedin FIGS. 1-4 has a number of drawbacks, which are avoided by the presentinvention as described below with respect to FIGS. 5-13. One drawback isthat the F-connection described above of each jet module 3 with theinlet manifold 7 a and outlet manifold 7 b, supplying the ink to all thejet modules in parallel, results in a relatively large mass in each jetmodule. This limits the operating frequency, and also the ink dropletsize, of the ink jet printer. The printer quality is thereby affected,as indicated earlier, since the print quality or resolution is enhancedby increasing the operating frequency and decreasing the size of the inkdroplets.

The quality of printing is also enhanced by close spacing of thenozzles. In the prior art construction illustrated by FIGS. 1-4, thecenter lines of the nozzles are generally spaced about 8 mm apart. Acloser spacing of the nozzles would enable higher quality printing aswell as a more compact printing head. In the prior construction, the jetprinting apparatus generally includes two printing head assemblies, eachas described above with respect to FIGS. 1-4, with the nozzles of oneassembly staggered with respect to the other assembly to enhance theprinting quality, but even more close spacing between the nozzle centerlines would even further enhance the printing quality.

A still further drawback in the prior art apparatus illustrated in FIGS.1-4 is the difficulty in cleaning the nozzles 5 at the printing sitewithout requiring major disassembly of the print head. Thus, it wasfound that dirt accumulating within passageway 14 was particularlydifficult to remove and significantly affected the operation of theapparatus unless it was thoroughly cleaned. This generally requiredsubstantial down-time of the apparatus and/or removal of the apparatusfor cleaning purposes.

As also indicated earlier, and as shown in FIG. 4, the prior artapparatus illustrated in FIGS. 1-4 includes a separate gutter 30 foreach nozzle 5. Such an arrangement increases the size of the printerhead assembly, and also the cost of its manufacture.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention, as described below with respect to theembodiments of FIGS. 5-8, 9-12 and 13, respectively, improves the jetprinting apparatus in one or more of the above respects.

The Embodiment of FIGS. 5-8

The embodiment illustrated in FIGS. 5-8 includes improvements over theprior art construction of FIGS. 1-4 in all of the above respects. Tofacilitate understanding the embodiment of FIGS. 5-8, the elementsthereof corresponding to the prior art construction of FIGS. 1-4 willgenerally be identified by the same reference numerals as in FIGS. 1-4,but increased by “100”.

Thus, the apparatus illustrated in FIGS. 5-8 also includes a commonmounting member 102 for mounting a linear array of jet modules 103 eachincluding an inlet 108 (FIG. 7) for receiving ink, an outlet 110 (shownin phantom in FIG. 7) for re-circulating the ink, a nozzle 105 fordischarging ink in the form of droplets, and a perturbation device inthe form of a piezoelectric transducer 106 for causing a continuousstream of ink droplets to be discharged from the respective nozzle. Forthis purpose, the common mounting member 102 is formed with an inletmanifold 107 a connected to an ink reservoir (not shown) for supplyingthe ink to all the jet module inlets 108 in parallel, and with an outletmanifold 107 b.

In this case, however, the jet modules 102 are connected in parallelbetween the manifold inlet 107 a and the manifold outlet 107 b, not byF-connections as described above with respect to FIGS. 1-4, but ratherby T-connections. For this purpose, the common mounting member 102 isnot disposed laterally of the linear array of jet modules 103, butrather is formed with a plurality of bores for receiving the lineararray of jet modules 103, as shown particularly in FIGS. 6 and 7. Inaddition, the inlet and outlet manifolds 107 a, 107 b are not verticallyaligned with each other, but rather are horizontally aligned. Further,as shown particularly in FIG. 7, the inlet manifold 107 a communicateswith the jet module horizontal inlet 108; the vertically-extendingpassageway 109 leading to nozzle inlet 104, and the jet modulehorizontal outlet (shown in phantom in FIG. 7 at 110), coaxial withinlet 108 and communicating with the manifold outlet 107 b forre-circulating the ink. The foregoing passageways 108, 109 and 110,communicating with the inlet manifold 107 a, the nozzle inlet 104, andthe outlet manifold 107 b are all formed in body member 111 of therespective jet module 103.

The foregoing construction, including a T-connection between each jetmodule 103 with the inlet manifold 107 a and outlet manifold 107 b,enables the mass of each jet module to be significantly reduced, therebypermitting operation of the printer at higher frequencies and withsmaller droplets. In addition, such a construction permits closerspacing of the center lines of the jet modules, if desired, for furtherenhancing the print quality. For example, whereas the prior artconstruction of FIGS. 1-4 provided a spacing of 8 mm, the constructionof FIGS. 5-8 permits a spacing of 5 mm.

As further shown in FIG. 7, each jet module also includes a holder forthe respective nozzle 105 and removably attached to the body member 111by threads 113 formed with a passageway 114 connecting the nozzle inlet104 of the respective jet module to its nozzle 105. Passageway 114includes a filter 115 for removing dirt particles from the ink beforereaching the nozzle. In this case, however, the holder for the nozzle105 is made of two sections 112 a, 112 b attachable to each other bythreads 112 c, with holder section 112 b receiving an O-ring 112 d atits connection with the respective nozzle 105. Such a constructionconveniently permits both the nozzle 105, and its holder 112 a-112 c tobe removed from the jet module, and the nozzle 105 to be removed fromits holder, for cleaning purposes whenever desired, thereby avoidinglong down-time periods that would be required for otherwise cleaningthese elements at the printing site, or for removing the apparatus toanother location for cleaning purposes.

The jet modules illustrated in FIGS. 5-7 may otherwise be ofsubstantially the same construction as described above with respect toFIGS. 1-4, including a stem 117 at the opposite to the nozzle 105 formounting the piezoelectric transducer 106 driven by electrode 118, and acounter-weight 119 separated from the piezoelectric transducer by aseparator disc 120.

As indicated earlier, and as shown in FIG. 4, the prior art printerincludes a separate gutter 30 for each nozzle 5, which increases thesize of the printer head assembly and also the cost of its manufacture.This drawback is avoided in the manner illustrated FIG. 8, wherein itwill be seen that the apparatus includes a gutter 130 which is shared byeach pair of jet module nozzles 105. Thus, in the constructionillustrated in FIG. 8, a gutter would be provided in every other spacebetween the jet modules such that each gutter is shared by two jetmodules on its opposite sides, thereby substantially reducing the sizeof the printer head assembly as well as of its cost of manufacture.

The Embodiment of FIGS. 9-12

FIGS. 9-12 illustrate a second embodiment of the invention which is, inmany respects, similar to that of FIGS. 5-8. To facilitateunderstanding, therefore, those elements in FIGS. 9-12 which generallycorrespond with those of FIGS. 5-8 are identified by the same referencenumerals, but in the “200” series.

Thus, the embodiment of FIGS. 9-12 also includes a mounting device,generally designated 202, for mounting a linear array of jet modules203. In this case, however, mounting device 202 is constituted of twosections 202 a, 202 b secured together with the array of jet modules 203inbetween. The two sections 202 a, 202 b are both made of plasticmaterial having relatively low mass as compared to the metal of the jetmodules. Such a construction thus permits the overall mass of each jetmodule to be reduced, thereby allowing operation at higher frequenciesand with smaller droplet sizes; at the same time, this constructionenables a larger spacing to be produced between the jet modules whendesired for purposes of reducing the overall cost of the jet modules.

As in FIGS. 5-8, each jet module 203 includes a nozzle inlet 204 (FIG.10) for receiving ink, a nozzle 205 for discharging ink in the form ofdroplets, and a perturbation device, in the form of a piezoelectrictransducer 206, for causing a continuous stream of ink droplets to bedischarged from the respective nozzle. The ink is supplied to the nozzleinlets 204 by an ink supply system including an inlet manifold, in theform of a passageway 207 a in mounting section 202 a, an outlet manifoldin the form of a passageway 207 b in mounting section 202 b, and aplurality of connecting passageways, as to be described below,connecting the nozzle inlets 204 in parallel between the inlet andoutlet manifolds. As will also be described below, such connectingpassageways connect each jet module between the inlet manifold 207 a andthe outlet manifold 207 b by a T-connection.

FIGS. 10 and 11 more particularly illustrate the inlet manifold 207 aformed in mounting section 202 a; the outlet manifold 207 b formed inmounting section 202 b; and the connecting passageways defining theT-connections between the jet modules. As shown particularly in FIG. 9,the inlet manifold 207 a in mounting section 202 a is supplied from theink reservoir (not shown) via a coupling 235, and is closed at itsopposite ends by plugs 236 a, 236 b; similarly, the outlet manifold 207b in mounting section 202 b is supplied from the ink reservoir viacoupling member 237 and is closed at its opposite ends by plugs 238 a,238 b.

For producing a T-connection of each jet module 203 with the inlet andoutlet manifolds 207 a, 207 b, the body member 211 of each jet module isformed with a transverse bore 240 communicating with the nozzle inlet204 of the respective jet module. In addition, the two mounting sections202 a, 202 b are each also formed with a bore 241 a, 241 b (FIG. 9) foreach jet module and aligned with bore 240 of the respective jet module.A plurality of pins 242, one for each jet module 203, are passed throughtheir respective bores 241 a of mounting section 202 a and arethreadedly received within one side of bore 240 of the respective jetmodule 203, for securing mounting section 202 a to one side of all thejet modules 203. Another set of pins 243, one for each jet module 203,are similarly passed through their respective bores 241 b in mountingsection 202 b and are threadedly received within the opposite side ofbore 240 of the jet modules 203 to secure mounting section 202 b to theprinting heads. As further shown in FIG. 9, the printer head assemblyfurther includes: O-rings 244 between pins 242 and mounting section 202a, O-rings 245 between mounting section 202 a and the respective side ofjet modules 203, O-rings 246 between the opposite of the jet modules andmounting section 202 b, and O-rings 247 between the latter mountingsection and the other group of pins 243.

It will thus be seen that the two sets of pins 242, 243 secure the twomounting sections 202 a, 202 b together with the linear array of jetmodules 203 inbetween. Pins 242, 243 also define, with the two mountingsections 202 a, 202 b and the jet modules 203 inbetween, theT-connection of each jet module with the inlet manifold 207 a inmounting section 202 a, and the outlet manifold 207 b in mountingsection 202 b.

The latter is more particularly illustrated in FIGS. 10 and 11. Thus, asparticularly shown in FIG. 11, each of the pins 242 is of reduced outerdiameter to define, with respect to bore 241 a, an axially-extendingspace 242 a on its outer surface between O-rings 244 and 245. Each pin242 is further formed with a radial bore 242 b establishingcommunication between space 242 a, and with an axial bore 242 c at theinner end of the pin and communicating with the nozzle inlet 204 forsupplying ink thereto. Similarly, the other set of pins 243 at theopposite side of the assembly also defines an axial space 243 a on itsouter surface between O-rings 246 and 247, a radial bore 243 b, and anaxial bore 243 c communicating with the jet module outlet forre-circulating the ink.

As further shown in FIG. 11, each of the manifolds 207 a, 207 b includesan opening, shown at 248 a, 248 b, respectively, for each jet module 203and communicating with the opposite sides of the jet module inlet 204via passageways 242 a, 242 b, 242 c at one side, and passageways 243 a,243 b, 243 c at the opposite side. Such an arrangement thereby defines aT-connection, similar to that of FIGS. 5-8, connecting each jet modulewith the inlet and outlet manifolds 207 a, 207 b.

Although the construction illustrated in FIGS. 9-12 does not include thetwo-part mounting for the nozzles 205 to facilitate their cleaning, asdescribed above with respect to FIGS. 5-8, it will be appreciated thatthis feature could also be included in the embodiment of FIGS. 9-12. Theembodiment of FIGS. 9-12 does include the filter 215, the O-ring 216,and the stem 217 at the opposite side of the body member 211 of each jetmodule 203 for mounting the perturbation device 206, and also formounting a counter-weight 219 separated from the perturbation device bya separator disc 220.

The Embodiment of FIG. 13

FIG. 13 illustrates a jet module, therein generally designated 303, ofthe prior art construction illustrated in FIG. 3, except that itincludes the two-part nozzle holder of FIGS. 5-8 for securing the nozzlein the manner permitting it to be conveniently disassembled and cleanedas and when desired without the need for extensively disassembling thejet module or removing it from operation for a substantial period oftime for purposes of cleaning the jet module.

Thus, as shown in FIG. 13, the holder for the nozzle 305 is constructedof a main section 312 a, a sleeve 312 b threadedly received on the mainsection by threads 312 c for conveniently removing the nozzle 305 fromthe holder as and when desired for cleaning purposes. The constructionillustrated in FIG. 13 further includes the O-ring 312 d between holdersection 312 c and the nozzle 305 for providing a sealed coupling withthe nozzle, as described above with respect to FIG. 7. The remainingconstruction may be as described above with respect to FIG. 3, andtherefore its parts are identified by the same reference numerals.

While the invention has been described above with respect to severalpreferred embodiments, it will be appreciated that these are set forthmerely for purposes of example, and that many other variations,modifications and applications of the invention may be made.

1. Inkjet printing apparatus, comprising: a linear array of jet moduleseach including an inlet for receiving ink, an outlet for re-circulatingthe ink, a nozzle for discharging ink in the form of droplets, and aperturbation device for causing a continuous stream of ink droplets tobe discharged from the respective nozzle; and an ink supply systemincluding an inlet manifold, an outlet manifold, and a plurality ofconnecting passageways connecting said jet modules in parallel betweenthe inlet and outlet manifolds; characterized in that said connectingpassageways connect the inlet of each jet module to said inlet manifoldand the outlet of each jet module to said outlet manifold, such as todefine a T-connection of each jet module with said inlet and outletmanifolds.
 2. The apparatus according to claim 1, wherein each of saidjet modules has a vertically-extending longitudinal axis, and whereinsaid inlet and outlet manifolds both have longitudinal axes extendinghorizontally, parallel to each other in a common horizontal plane onopposite sides of said jet modules.
 3. The apparatus according to claim1, wherein said linear array of jet modules is carried by a mountingdevice formed with said inlet and outlet manifolds.
 4. The apparatusaccording to claim 3, wherein each of said jet modules is formed with aT-shaped connecting passageway having a horizontal leg communicating atits opposite ends with said inlet and outlet manifolds, and a verticalleg centrally off said horizontal leg and leading to its respectivenozzle.
 5. The apparatus according to claim 3, wherein said perturbationdevice for each jet module is a piezoelectric transducer, and whereineach jet module is further formed with a mounting for said piezoelectrictransducer above the jet module inlet.
 6. The apparatus according toclaim 5, wherein each jet module further includes a counterweightsupported thereon above said piezoelectric transducer.
 7. The apparatusaccording to claim 3, wherein said mounting device is formed with alinear array of bores receiving said linear array of jet modules withsaid inlet and outlet manifolds of said mounting member located onopposite sides of said jet modules.
 8. The apparatus according to claim3, wherein said mounting device includes two sections secured togetherwith said array of jet modules inbetween.
 9. The apparatus according toclaim 8, wherein one of said sections includes said inlet manifold inthe form of a continuous channel plugged at its opposite ends, and theother of said sections includes said outlet manifold also in the form ofa continuous channel plugged at its opposite ends.
 10. The apparatusaccording to claim 9, wherein each of said sections is formed with anopening for each of said jet modules and includes a pin in each of saidopenings formed with a connecting passageway connecting the respectivemanifold to the respective side of the jet module inlet.
 11. Theapparatus according to claim 9, wherein said two sections of themounting device are made of a plastic material having a relatively lowmass.
 12. The apparatus according to claim 1, wherein each of said jetmodules includes a filter between its inlet and nozzle.
 13. Theapparatus according to claim 1, wherein each of said nozzles isremovably attached to the jet module by a coupling sleeve which permitsconvenient detaching of the nozzle for cleaning purposes.
 14. Theapparatus according to claim 1, wherein said jet modules are equallyspaced from each other in said linear array; and wherein said apparatusfurther includes a gutter in every other space between said jet modulessuch that each gutter is shared by two jet modules on the opposite sidesof the respective gutter.
 15. Ink jet printing apparatus, comprising: alinear array of jet modules each including an inlet for receiving ink,an outlet for re-circulating the ink, a nozzle for discharging ink inthe form of droplets, and a perturbation device for causing a continuousstream of ink droplets to be discharged from the respective nozzle; andan ink supply system including an inlet manifold, an outlet manifold,and a plurality of connecting passageways connecting said jet modules inparallel between the inlet and outlet manifolds; each of said nozzlesbeing removably attached to the jet module by a coupling sleeve whichpermits convenient detaching of the nozzle for cleaning purposes. 16.The apparatus according to claim 15, wherein said connecting passagewaysconnect the inlet of each jet module to said inlet manifold and theoutlet of each jet module to said outlet manifold, such as to define aT-connection of each jet module with said inlet and outlet manifolds.17. The apparatus according to claim 16, wherein each of said jetmodules has a vertically-extending longitudinal axis, and wherein saidinlet and outlet manifolds both have longitudinal axes extendinghorizontally parallel to each other in a common horizontal plane onopposite sides of said jet modules.
 18. Ink jet printing apparatus,comprising: a linear array of jet modules each including an inlet forreceiving ink an outlet for re-circulating the ink, a nozzle fordischarging ink in the form of droplets, and a perturbation device forcausing a continuous stream of ink droplets to be discharged from therespective nozzle; each of said jet modules being equally spaced fromeach other in said linear array; an ink supply system including an inletmanifold, an outlet manifold, and a plurality of connecting passagewaysconnecting said jet modules in parallel between the inlet and outletmanifolds; and a gutter in every other space between said jet modulessuch that each gutter is shared by two jet modules on its oppositesides.
 19. The apparatus according to claim 18, wherein said connectingpassageways connect the inlet of each jet module to said inlet manifoldand the outlet of each jet module to said outlet manifold, such as todefine a T-connection of each jet module with said inlet and outletmanifolds.
 20. The apparatus according to claim 19, wherein each of saidjet modules has a vertically-extending longitudinal axis, and whereinsaid inlet and outlet manifolds both have longitudinal axes extendinghorizontally parallel to each other in a common horizontal plane onopposite sides of said jet modules.